Electrostatic-piezoelectric transducer

• US 3,894,198 A
• Filed: 11/06/1972
• Issued: 07/08/1975
• Est. Priority Date: 11/04/1971
• Status: Expired due to Term

• Current Assignee: Haohiro Murayama, Kenichi Nakamura, Takao Oikawa
• Original Assignee: Haohiro Murayama, Kenichi Nakamura, Takao Oikawa
• Inventors: Oikawa, Takao, Nakamura, Kenichi, Murayama, Haohiro
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Stellar, George G.
• Application Number:
  US05/303,894
• Time in Patent Office: 974 Days
• Field of Search: 179/11A,111R,111E,106,108,11F 310/8.6,8.3 317/144 307/88ET
• US Class Current: 381/114
• CPC Class Codes: H04R 17/005 using a piezoelectric polymer
• CPC Class Codes: H04R 19/013 for loudspeakers
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

An electrostatic type electroacoustic transducer having improved acoustic characteristics is composed of a piezoelectric polymertype oscillator having a stretching-type piezoelectric effect, such as a polarized polyvinylidene fluoride film having electrodes vacuum-coated on both surfaces and at least one fixed electrode disposed facing the oscillator and spaced therefrom.

Claims

1. An electrostatic type electroacoustic transducer comprising:

a. oscillator means fixed at two portions thereof and including a piezoelectric polymer sheet having stretching-type piezoelectric characteristics and electrodes on both surfaces of said polymer sheet;

b. at least one fixed electrode means facing said oscillator means and spaced therefrom; and

c. means for applying an alternating current electric input signal to both said oscillator and said electrode means, said oscillator means and said fixed electrode means being positioned such that, upon application of the input signal, the oscillating movement of said oscillator means is intensified by the combination of;

the bowing of said oscillator means between the two fixed portions thereof, said bowing being caused by the piezoelectric effect of the piezoelectric polymer sheet; and

the attractive and repulsive forces between said oscillator means and said fixed electrode means.

2. The electrostatic type electroacoustic transducer as claimed in claim 1 wherein said piezoelectric polymer sheet is a piezoelectric vinylidene fluoride resin sheet.

3. The electrostatic type electroacoustic transducer as claimed in claim 1 wherein said fixed electrode means comprises an electret having a conductor backing plate.

4. The electrostatic type electroacoustic transducer as claimed in claim 1 wherein said fixed electrode means comprises two fixed electrodes, one on each side of said oscillator means whereby said fixed electrode means exerts a push-pull effect on said oscillator means.